The quake occurred 40 km southwest of the coastal city of Ourika, but no tsunami warning was issued.
In a preliminary assessment, the center said that the possibility of deaths or injuries is low, but material damage is possible.
The National Tsunami Warning Center confirmed that no tsunami was expected.
The power grid was affected by the earthquake, and a specialized website stated that power was cut off from 60,000 homes in Humboldt County.
And the emergency services in the province, whose largest city is Eureka, wrote in a message via Twitter that “the power was cut off throughout the province.”
California regularly witnesses earthquakes, and seismologists warn that it is almost certain that an earthquake capable of causing widespread destruction will strike this state within the next 30 years.
In 1994, a 6.7-magnitude earthquake in Northridge, northwest of Los Angeles, killed at least 60 people and caused an estimated $10 billion in damage, while a 6.9-magnitude earthquake in San Francisco in 1989 killed 67 people.
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